Wireless force sensor on a distal portion of a surgical instrument and method

ABSTRACT

A surgical instrument includes a distal portion. A force sensor is operatively mounted on the distal portion. The force sensor includes a wireless package, which wirelessly provides (1) identification information of the surgical instrument and (2) strain data related to the distal portion. A surgical end effector includes a jaw and the distal portion is on a non-contact portion of the jaw. The wireless package includes a surface acoustic wave strain sensor with identification information. The wireless package also includes a small folded antenna electrically coupled to the surface acoustic wave strain sensor with identification information. The identification information includes an identification of a type of surgical instrument and unique identification of the specific surgical instrument in the type of surgical instrument.

CROSS-REFERENCE TO RELATED APPLICATIONS AND PATENTS

This application is a continuation of U.S. patent application Ser. No.14/107,692 (filed Dec. 16, 2013), which is a continuation of U.S. patentapplication Ser. No. 12/634,489 (filed 9 Dec. 2009, now U.S. Pat. No.8,628,518 B2), which is continuation-in-part of U.S. patent applicationSer. No. 11/864,974 (filed Sep. 29, 2007, now U.S. Pat. No. 8,375,808B2), which is a continuation-in-part of U.S. application Ser. No.11/537,241 (filed Sep. 29, 2006, now U.S. Pat. No. 8,945,095 B2), whichclaims priority to and the benefit of U.S. Provisional Application No.60/755,108 (filed Dec. 30, 2005), all of which are incorporated byreference herein in their entireties for all purposes.

TECHNICAL FIELD

The present invention relates generally to minimally invasive surgicalsystems, e.g., minimally invasive teleoperated robotic surgical systems,and, more particularly, to an improved apparatus, and method for sensingforces applied by a surgical instrument.

BACKGROUND

In teleoperated robotically assisted surgery, the surgeon typicallyoperates a master controller to control the motion of surgicalinstruments at the surgical site from a location that may be remote fromthe patient (e.g., across the operating room, in a different room or acompletely different building from the patient). The master controllerusually includes one or more hand input devices, such as handheld wristgimbals, joysticks, exoskeletal gloves, handpieces, or the like, whichare operatively coupled to the surgical instruments through a controllerwith servo motors for articulating the instruments' position andorientation at the surgical site.

The servo motors are typically part of an electromechanical device orsurgical manipulator arm (“the slave”) that includes a plurality ofjoints, linkages, etc., that are connected together to support andcontrol the surgical instruments that have been introduced directly intoan open surgical site or through trocar sleeves (cannulas) insertedthrough incisions into a body cavity, such as the patient's abdomen.There are available a variety of surgical instruments, such as tissuegraspers, needle drivers, electrosurgical cautery probes, etc., toperform various functions for the surgeon, e.g., retracting tissue,holding or driving a needle, suturing, grasping a blood vessel,dissecting, cauterizing, coagulating tissue, etc. A surgeon may employ alarge number of different surgical instruments/tools during a procedure.

This new surgical method through remote manipulation has created manynew challenges. One challenge is providing the surgeon with the abilityto accurately “feel” the tissue that is being manipulated by thesurgical instrument via the robotic manipulator. The surgeon must relyon visual indications of the forces applied by the instruments orsutures.

Various attempts to measure the forces and torques and to providefeedback to a surgeon have been made. One device for this purpose fromthe laboratory of G. Hirzinger at DLR Institute of Robotics andMechatronics is described in “Review of Fixtures for Low-InvasivenessSurgery” by F. Cepolina and R. C. Michelini, Int'l Journal of MedicalRobotics and Computer Assisted Surgery, Vol. 1, Issue 1, page 58, thecontents of which are incorporated by reference herein for all purposes.However, that design disadvantageously places a force sensor distal to(or outboard of) the wrist joints, thus requiring wires or optic fibersto be routed through the flexing wrist joint and also requiring the yawand grip axes to be on separate pivot axes.

As described in A. Dalhlen et al., “Force Sensing Laparoscopic Grasper,”U. Wisconsin Coll. Eng., Apr. 28, 2006(http://homepages.cae.wisc.edu/˜bme402/grasping_instruments_06/reports/Final_Paper.pdf),a team at the Univ. of Wisconsin led by A. Dahlen and advised by W.Murphy considered strain gauges on several parts of the jaw actuationmechanism of a manual laparoscopic bowel grasper finally settling on thehand grip. Also, as described at Paragraph 4.2, Medical Robotics, I-TechEducation and Publishing, Vienna, Austria, Pg. 388, (2007) (ISBN 13:978-3-902613-18-9), U. Seibold et al at the German DLR Institutesimilarly measured the gripper actuation cable tension to calculate thegrip force.

F. van Meer at LAAS/CNRS (2004) in Toulouse France pursued and patentedwhat is described as a MEMS 2D silicon force sensor cemented to theinner surfaces of opposing folded sheet metal jaws of a five millimeter(mm) instrument and connected by ten wires. The sensor is capacitive andrequires capacitive readout electronics located nearby. See Van Meer, etal., “2D Silicon Macro-force Sensor For a Tele-operated SurgicalInstrument,” Proc. 2004 Int'l Conf. on MEMS, Nano and Smart Systems,(2004) (ICMENS-04). U.S. Pat. No. 6,594,552 to Nowlin et al. (2003)describes a method of governing grip force without jaw sensors andinstead is based on a position control loop of the instrument jaws withthe robot master grip command force dependent on springs resistingclosure of the master finger levers.

G. Fischer et al., at Johns Hopkins University, (2006) attached straingauges and blood oxygen sensors with lead wires to the leaves of a fanretractor to measure surgical forces (not grip forces) and resultingischemia in liver tissue. See Fischer et al, “Ischemia and Force SensingSurgical Instruments for Augmenting Available Surgeio Information,”ERCCIS-JHU Int'l Conf. on Biomedical Robotics and Biomechatronics(BioRob) (February 2006).

E. Dutson et al., at UCLA, (2005) applied wire connected pressuresensing pads to the inner faces of a daVinci robotic surgical instrumentand displayed the resulting contact force signal to the surgeon using apneumatically actuated pad on the robot master finger levers. See DutsonE P, Hwang R, Douraghy A, Mang J, Vijayaraghavan A, Gracia C, GrundfestN, “Haptic feedback system for robotic surgery,” Society of AmericanGastrointestinal and Endoscopic Surgeons (SAGES) 2005 Annual Meeting,Ft. Lauderdale, Fla., (Apr. 13-16, 2005).

U.S. Pat. No. 7,300,450 to Petronella et al. (2007) describes alaparoscopic instrument with a jaw force sensor comprising an opticfiber passing into a moveable jaw and aimed a reflecting surface on thejaw so that the amount of light reflected varies with the force on thelaw.

Each of these methods has shortcomings. For example, gripper jawactuator cable forces do not measure the effects of jaw pivot frictionwk ich rises as the law actuation force increases. Contact sensorsapplied to the instrument jaw working face are subject to high contactpressures that may damage the sensor. An optic fiber or wires passingthrough the instrument wrist to a jaw sensor is liable to breakage.

SUMMARY

An apparatus and method improve force feedback to a surgeon performing aminimally invasive surgery such as a minimally invasive teleoperatedrobotic surgery. A surgical instrument includes a distal portion. Aforce sensor is operatively mounted on the distal portion. The forcesensor includes a wireless package, which wirelessly provides (1)identification information of the surgical instrument and (2) straindata related to the distal portion.

The surgical instrument also includes a wrist joint and a surgical endeffector mounted distal to the wrist joint of the surgical instrument.The distal portion is on the surgical end effector in one aspect. Inanother aspect, the distal portion is proximal to the wrist joint.

In one embodiment, the surgical end effector includes a jaw and thedistal portion is on the law. The jaw can be made of an electricallynon-conductive material.

The wireless package includes a surface acoustic wave strain sensor withidentification information. The surface acoustic wave strain sensorincludes identification information of the surgical instrument. Thewireless package also includes, in one embodiment, a small foldedantenna electrically coupled to the surface acoustic wave strain sensorwith identification information. In another embodiment, the antenna is anon-folded antenna.

In one aspect, the small folded antenna and the surface acoustic wavestrain sensor have a common surface on a substrate and are electricallyconnected by one of trace wire connections and bond wire connections. Inanother aspect, the folded antenna is on a first surface of a substrateand the surface acoustic wave strain sensor is on a second surface ofthe substrate. The second surface is opposite and removed from the firstsurface. In yet another aspect, the folded antenna and the surfaceacoustic wave strain sensor are on different substrates, and areelectrically connected.

The identification information includes an identification of a type ofsurgical instrument. The identification information further includesunique identification of one and only one surgical instrument in thetype of surgical instrument.

In another aspect, this surgical instrument is included in an apparatusthat also includes an interrogator antenna. The interrogator antenna isconfigured to transmit wireless interrogation signals to the wirelesspackage, and to receive wireless signals, from the wireless package,containing the strain data and identification information. The apparatusfurther includes a wireless interrogator, coupled to the interrogatorantenna, to provide signals to the interrogator antenna and to receivesignals from the interrogator antenna.

In one aspect, the interrogator antenna is located external to a patientundergoing surgery. In another aspect, the interrogator antenna ismounted on another surgical instrument so that when a patient isundergoing surgery, the interrogator antenna is internal to the patient.

The apparatus also includes a computer connected to the wirelessinterrogator to analyze a signal including (1) identificationinformation of the surgical instrument and (2) strain data from thedistal portion, and to convert the strain data into a force signal. Theforce signal is used to provide feedback to a surgeon operating thesurgical instrument.

A method of using the force sensor receives a wireless interrogationsignal in a wireless package mounted on a distal portion of a surgicalinstrument. The method further includes wirelessly transmitting from thewireless package, in response to the interrogation signal, (1)identification information of the surgical instrument and (2) straindata from the distal portion.

The scope of the invention is defined by the claims, which areincorporated into this section by reference. A more completeunderstanding of embodiments of the present invention will be affordedto those skilled in the art, as well as a realization of additionaladvantages thereof, by a consideration of the following detaileddescription of one or more embodiments. Reference will be made to theappended sheets of drawings that will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a minimally invasive surgical system inaccordance with an embodiment of the present invention.

FIG. 1B is a perspective view of a minimally invasive surgical arm cartsystem of the minimally invasive surgical system in FIG. 1A inaccordance with an embodiment of the present invention.

FIG. 1C is a front perspective view of a master console of the minimallyinvasive surgical system in FIG. 1A in accordance with an embodiment ofthe present invention.

FIG. 2A is a perspective view of a surgical instrument including awireless force sensor operatively mounted on a distal portion of thesurgical instrument in accordance with an embodiment of the presentinvention.

FIGS. 2B to 2D are views of a first aspect of the wireless force sensorof FIG. 2A.

FIG. 2E to 2G are views of a second aspect of the wireless force sensorof FIG. 2A that includes a chirped surface acoustic wave strain sensorwith identification information.

FIG. 3A is a block diagram of one aspect of a force sensor that includesa wireless package, which wirelessly provides (1) identificationinformation of a surgical instrument and (2) strain data.

FIG. 3B is a block diagram of another aspect of a force sensor thatincludes a wireless package, which wirelessly provides (1)identification information of a surgical instrument and (2) strain data.

FIG. 3C illustrates a wireless package that includes a small foldedantenna and a surface acoustic wave strain sensor with identificationinformation on a common substrate.

FIG. 3D illustrates a wireless package that includes an antenna and asurface acoustic wave strain sensor with identification information inseparate packages that are connected together.

FIG. 3E illustrates a top view of a wireless package that includes asmall folded antenna and a surface acoustic wave strain sensor withidentification information with the small folded antenna on a firstsurface of a common substrate.

FIG. 3F illustrates a bottom view of a wireless package that includes asmall folded antenna and a surface acoustic wave strain sensor withidentification information with the strain sensor on a second surface ofthe common substrate.

FIG. 3G illustrates a chirped surface acoustic wave strain sensor withidentification information for a wireless package.

FIG. 4A is a more detailed block diagram of aspects of a minimallyinvasive surgical system that includes a wireless force sensor and aninterrogator antenna, external to a patient, to provide a wirelessinterrogation signal.

FIG. 4B is a more detailed block diagram of aspects of a minimallyinvasive surgical system that includes a wireless force sensor and aninterrogator antenna, mounted on another minimally invasive surgicalinstrument, to provide a wireless interrogation signal internal to apatient.

FIG. 5 is a perspective view of a surgical instrument including a forcesensor apparatus operably coupled proximal (or inboard) to a wrist jointin accordance with an embodiment of the present invention.

FIG. 6A is a perspective view of a surgical instrument distal endshowing a wrist, grip jaws, and force sensors for use with a teleroboticsurgical system.

FIG. 6B is a first top view of the surgical instrument of FIG. 6Ashowing applied forces.

FIG. 6C is a first side view of the surgical instrument of FIG. 6Ashowing applied forces.

FIG. 6D is a second top view of the surgical instrument of FIG. 6Ashowing applied torque.

FIG. 6E is a second side view of the surgical instrument of FIG. 6Ashowing applied torque.

Embodiments of the present invention and their advantages are bestunderstood by referring to the detailed description that follows. Itshould be appreciated that like reference numerals are used to identifylike elements illustrated in one or more of the figures. It should alsobe appreciated that the figures may not be drawn to scale.

DETAILED DESCRIPTION

A multi-component minimally invasive surgical system 100 (FIGS. 1A to1C), e.g., a teleoperated robotic surgical system, and method senseforces applied to tissue, sutures, needles, clips, and the like via adistal end of a surgical instrument while performing, for example,teleoperated robotically assisted surgical procedures on a patient,particularly including open surgical procedures, neurosurgicalprocedures, and minimally invasive procedures, such as laparoscopy,arthroscopy, thoracoscopy, and the like. A wireless force sensor 275(FIG. 2A) mounted on a distal portion of a surgical instrument 230 isparticularly useful as part of a minimally invasive surgical system 100that allows surgeon 190 to manipulate surgical instruments through aservomechanism from a location 110 remote from the patient.

To that end, the combined manipulator apparatus or slave and surgicalinstrument of the present invention is usually driven by a master havingthe same degrees of freedom (e.g., three degrees of freedom for positionand three degrees of freedom for orientation plus grip) to form atelepresence system with force reflection or other scalar forcemagnitude display. A description of a suitable slave-master system canbe found in U.S. Pat. No. 6,574,355, the complete disclosure of which isincorporated herein by reference for all purposes.

In FIGS. 1A to 1C, minimally invasive surgical system 100 is illustratedthat includes at least one surgical instrument 230 (FIGS. 2A to 2G)having, in one aspect, a wireless force sensor 275, mounted on a distalportion of surgical instrument 230, as described more completely below.In one aspect, the distal portion is proximal to a wrist joint, and inanother aspect, the distal portion is distal to the wrist joint. SeeFIGS. 2A to 2G and FIG. 5.

As explained more completely below, wireless force sensor 275 includes awireless package, which in response to a received wireless interrogationsignal measures strain in the distal portion and wirelessly transmits(1) identification information of surgical instrument 230 (FIGS. 2A to2G) and (2) strain data from the distal portion to an interrogatorantenna in the operating room. In this example, the interrogator antennais included in a wireless interrogator unit 160 attached to display 150(FIG. 1A). In one aspect, the strain data is processed to providereal-time force feedback to surgeon 190 in the surgical robot master'sfinger grips and in another aspect in a display viewed by surgeon 190.

Surgeon 190 using a surgical instrument including wireless force sensor275 is able to sense, for example, the jaw grip force of variousgraspers and needle drivers to avoid damaging tissue, sutures orneedles. The real-time force feedback also allows surgeon 190 tomodulate the grip force to improve execution of various surgical taskswhile avoiding these types of damage.

Wireless communication is the transfer of information over a distancewithout the use of electrical conductors or wires. Similarly, a wirelesssignal is a signal that travels over the distance of the wirelesscommunication without the use of electrical conductors or wires.

The wireless communication eliminates the prior art need for wires fromdifficult locations on a surgical instrument. The wireless communicationalso eliminates the need for additional electrical contacts at thesterile adapter interface. In particular, the need for contacts capableof a sufficiently clean signal for strain sensing is eliminated.Finally, the wireless communication and the operation of wireless forcesensor 275 at high frequencies (e.g., GHz) provides immunity to cauterynoise without resorting to fiber optic strain sensing which would besignificantly more difficult at the jaw location than as presentlyperformed on the instrument shaft.

As shown in FIGS. 1A through 10, minimally invasive surgical system 100generally includes one or more surgical manipulator assemblies 120 to123 mounted to or near an operating table and a master control assemblylocated at a surgeon's console 110 (FIGS. 1A and 1C) for allowing asurgeon to view the surgical site and to control manipulator assemblies120 to 123. System 100 also includes one or more viewing scopeassemblies 131 and a plurality of surgical instrument assemblies adaptedfor being removably coupled to manipulator assemblies 120 to 123, asdiscussed in more detail below. Minimally invasive surgical system 100includes at least two manipulator assemblies and preferably at leastthree manipulator assemblies. The exact number of manipulator assembliesdepends on the surgical procedure and the space constraints near thepatient among other factors.

A control assembly may be located at surgeon's console 110, which isusually located in the same room as the operating table so that surgeon190 may speak to his/her assistant(s) and directly monitor the operatingprocedure. However, it should be understood that the surgeon 190 can belocated in a different room or a completely different building from thepatient.

The master control assembly generally includes a support, a monitor fordisplaying an image of the surgical site to surgeon 190, and one or moremaster(s) for controlling manipulator assemblies 120 to 123. Master(s)may include a variety of input devices, such as hand-held wrist gimbals,joysticks, gloves, trigger-guns, hand-operated controllers, voicerecognition devices, or the like. Preferably, master(s) are providedwith the same degrees of freedom as the combined manipulator andsurgical instrument assembly. In this aspect, the masters include acapability to provide force feedback based on the wireless strain datafrom the distal portion of surgical instrument 230.

In conjunction with the endoscopic view, this provides surgeon 190 withtelepresence, the perception that the surgeon is immediately adjacent toand immersed in the surgical site, and intuitiveness, the perceptionthat the master(s) are integral with the surgical instruments so thatsurgeon 190 has a strong sense or directly and intuitively controllingthe surgical instruments as if the instruments are part of, or held inhis/her hands. Position, force, and tactile feedback sensors (not shown)may also be employed on the surgical instrument assemblies to transmitposition, force, and tactile sensations from the surgical instrumentback to the surgeon's hands, ears, or eyes as he/she operates minimallyinvasive surgical system 100. One suitable system and method forproviding telepresence to the operator is described in U.S. Pat. No.6,574,355, which has previously been incorporated herein by reference.

Monitor 111 (FIG. 1C) is suitably coupled to viewing scope assembly 131such that an image of the surgical site is provided adjacent thesurgeon's hands on surgeon console 110. Preferably, monitor 111 displaysan image that is oriented so that surgeon 190 feels that he or she isactually looking directly down onto the surgical site. To that end, animage of surgical instruments appears to be located substantially wherethe surgeon's hands are located. In addition, the real-time image is astereoscopic image such that the surgeon can manipulate a surgical endeffector of a surgical instrument via the hand control as if viewing theworkspace in substantially true presence. The image simulates theviewpoint or orientation of a surgeon who is physically manipulating thesurgical instrument.

A servo control is provided for transferring the mechanical motion ofmasters to manipulator assemblies 120 to 123. The servo control may beseparate from, or integral with, manipulator assemblies 120 to 123. Theservo control provides force feedback and, in some aspects, torquefeedback from surgical instruments to the hand-operated masters, inaddition, the servo control may include a safety monitoring controller(not shown) to safely halt system operation, or at least inhibit allrobot motion, in response to recognized undesirable conditions (e.g.,exertion of excessive force on the patient, mismatched encoder readings,etc.).

The servo control preferably has a servo bandwidth with a 3 dB cut offfrequency of at least 10 Hz so that the system can quickly andaccurately respond to the rapid hand motions used by the surgeon and yetto filter out undesirable surgeon hand tremors. To operate effectivelywith this system, manipulator assemblies 120 to 123 have a relativelylow inertia, and the drive motors have relatively low ratio gear orpulley couplings. Any suitable conventional or specialized servo controlmay be used in the practice of the present invention, with thoseincorporating force and torque feedback being particularly preferred fortelepresence operation of the system.

Referring to FIG. 2A, a perspective view is shown of a surgicalinstrument 230 including a wireless force sensor 275 operably mounted ondistal end portion of a surgical end effector 240. Surgical end effector240 is coupled to a wrist, joint 220 that in turn is connected to arigid shaft 210. A housing 250 is operably coupled to a proximal end ofrigid shaft 210, and includes a sterile adapter interface 252, whichmechanically and electrically couples instrument 230 to any one ofmanipulator assembly sterile adapters 130, 132, 133. While in thisillustration wireless force sensor 275 is distal to wrist joint 220, insome aspects, wireless force sensor 275 can be mounted proximal to wristjoint 220.

Also, in some aspects, when surgical instrument 230 is not in use and isexternal to the patient, a radio frequency shielded pocket 255 is placedover end effector 240. Radio frequency shielded pocket 255 isconstructed and sized so that when pocket 255 is mounted on surgicalinstrument 230, the radio frequency shielding of pocket 255 shieldswireless force sensor 275 from wireless interrogation signals. Thetemperature stabilization features, described more completely below, mayalso be incorporated in radio frequency shielded pocket 255.

Applicable housings, sterile adaptor interfaces, and manipulator armsare disclosed in U.S. Patent Application Publication No. 2006/0161138 A1on Jul. 20, 2006 for U.S. patent application Ser. No. 11/314,040 filedon Dec. 20, 2005, and U.S. Patent Application Publication No.2007/0137371 A1 on Jun. 21, 2007 for U.S. application Ser. No.11/613,800 filed on Dec. 20, 2006, the full disclosures of which areincorporated by reference herein for all purposes. Examples ofapplicable shafts, end portions, housings, sterile adaptors, andmanipulator arms are manufactured by Intuitive Surgical, Inc. ofSunnyvale, Calif.

FIGS. 2B to 2G are close-up magnified illustrations of surgical endeffector 240, which in this example includes two jaws. Surgical endeffector 240 has a range of motion that includes pitch and yaw motionabout the x- and y-axes and rotation about the z-axis. These motions aswell as actuation of a surgical end effector are provided via cables inhousing 250 and cables and/or rods running through shaft 210 and intohousing 250 that transfer motion from the manipulator assembly.Embodiments of drive assemblies, arms, forearm assemblies, adaptors, andother applicable parts are described for example in U.S. Pat. Nos.6,331,181, 6,491,701, and 6,770,081, the full disclosures of which areincorporated herein by reference for all purposes.

As shown in FIGS. 2B to 2D, wireless force sensor 275A includes awireless package 270A that is mounted on a distal portion of surgicalend effector 240A. As shown in FIGS. 2C and 2D, wireless package 270A ismounted in a recess on a non-contact surface of one jaw 241A of the pairof jaws of surgical end effector 240A. In this aspect, wireless package270A (FIG. 2D) includes two components, a surface acoustic wave strainsensor with identification information 290A and a small folded antenna280A. All or part of wireless package 270A may also be mounted on anon-recessed non-contact surface and provided with adequate physicalprotection.

As shown in FIGS. 2E to 2G, wireless force sensor 275B also includes awireless package 270E that is mounted on a distal portion of surgicalend effector 240B. Wireless package 270B is mounted in a recess thatextends along the length of a non-contact surface of one jaw 241B of thepair of jaws of surgical end effector 240B. In this aspect, wirelesspackage 270B (FIGS. 2F and 2G) includes two components, a chirpedsurface acoustic wave strain sensor with identification information 290Eand a small folded antenna 280B. All or part of wireless package 270Amay also be mounted on a non-recessed non-contact surface and providedwith adequate physical protection. As explained more completely below,chirped surface acoustic wave strain sensor 2903 allows determination ofboth the force applied by jaws and the location of that force as well astemperature compensation.

As used herein, a small folded antenna refers to a folded antenna thatis of a size that can be mounted on surgical instrument 230 (FIG. 2A) inthe vicinity of the surface acoustic wave strain sensor and notinterfere with the operation of surgical instrument 230. Examples ofsmall folded antennas include, but are not limited to, a fractal (e.g.Hilbert, Sierpinski, etc.) antenna, a folded antenna designed usinggenetic algorithms, a crankline antenna, a micro-strip meander antenna,a compact diversity antenna or other minimum size antenna for a givenwireless interrogation signal. A non-folded antenna may also be usedwhere space permits as on instrument tube 210 (FIG. 2A), for example.

Surface acoustic wave strain sensor with identification information 290A(FIGS. 20 and 20), 290B (FIGS. 2F and 2G) in turn includes at least aninterdigital transducer (IDT) 291A (FIGS. 2C and 2D), 291B (FIGS. 2F and2G) and a portion 292A, 292B that includes reflectors that provide bothstrain data and identification information. As is known to thoseknowledgeable in the field, other components may be used to couple smallfolded antenna 280A, 280B to surface acoustic wave strain sensor withidentification information 290A, 290C. For example, wireless package270A, 270C can include an impedance matching network, i.e. tuningcomponents such as capacitors and inductors to improve signal couplingto/from wireless interrogator 160 thru antenna 280A, 280C from/tosurface acoustic wave strain sensor 290A, 290C.

In one aspect, a wireless interrogation signal, e.g., a 2.4 GHz signal,emitted from interrogation unit 160 (FIG. 1A), is received by antenna280A (FIG. 29) and/or antenna 280B (FIG. 2G). In the followingdescription, the embodiment of FIGS. 2B to 2D is used, but thedescription is also applicable to the embodiment of FIGS. 2E to 2G. Inresponse to the wireless interrogation signal, antenna 280A supplies anelectrical signal to interdigital transducer (IDT) 291A. Interdigitaltransducer 291A transforms the received signal into a surface acousticwave (SAW). The surface acoustic wave propagates along the substratefrom interdigital transducer 291A towards the reflectors. Each reflectorreflects part of the incoming surface acoustic wave. The reflectors areplaced in a specific pattern so that the reflected waves provide theidentification information and provide strain data. Thus, the strainsensors are sometimes referred to as surface acoustic wave strainsensors with identification information. The identification informationis effectively encoded in the reflector positioning. The number ofreflectors shown herein is illustrative only and is not intended to belimiting to the particular configuration illustrated.

The reflected surface acoustic waves are received by interdigitaltransducer 291A and are converted back into an electrical signal that isapplied to antenna 280A. Antenna 280A radiates a wireless responsesignal back to interrogation unit 160. The wireless response signalincludes strain data and identification information of surgicalinstrument 230.

Various implementations of wireless packages 270A, 270B and the strainand information reflectors in a surface acoustic wave strain sensor canbe utilized. Each of the embodiments discussed more completely below isillustrative only and is not intended to be limiting to the particularaspects presented. In view of these examples, those knowledgeable in thefield can implement combinations other than those shown to facilitateuse of at least one wireless force sensor on a minimally invasivesurgical instrument.

FIG. 3A is a block diagram of one aspect of a wireless force sensor 375Athat includes a wireless package 370A, which wirelessly provides (1)identification information of a surgical instrument and (2) strain data.Wireless package 370A is an integrated package that includes a smallfolded antenna 380A and a surface acoustic wave strain sensor withidentification information 390A. Surface acoustic wave strain sensorwith identification information 390A, in turn, includes at least aninterdigital transducer 391A, surface acoustic wave identification (ID)information reflectors 393A and surface acoustic wave strain sensorreflectors 394A. Strain sensor 390A could also include an impedancematching network, as described above.

Surface acoustic wave identification (ID) information reflectors 393Agenerate reflected waves representing the identification information ofthe surgical instrument on which wireless package 370A is mounted.Surface acoustic wave strain sensor reflectors 394A generate reflectedwaves representing strain data from the distal portion of the surgicalinstrument on which surface acoustic wave strain sensor 390A is mounted.

The relative locations of reflectors 393A and 394A are illustrative onlyand are not intended to be limiting to these specific locations. Forexample, reflectors 393A could be positioned after reflectors 394Ainstead of before reflectors 394A as shown in FIG. 3A. Also, in place ofreflectors 393A and 394A being arranged serially in a line along anx-axis as shown in FIG. 3A, the two sets of reflectors could be arrangedin a stacked configuration (e.g., in two or more parallel rows) alongthe y-axis. The particular orientation is not essential so long as bothidentification information and strain data can be generated.

Also, it is not necessary to use two distinct sets of reflectors. Asingle set of reflectors can generate both identification informationand strain data. For example, FIG. 3B is a block diagram of anotheraspect of a wireless force sensor 375B that includes a wireless package375B, which wirelessly provides (1) identification information of asurgical instrument and (2) strain data. Wireless package 370B includesa small folded antenna 380E and a surface acoustic wave strain sensorwith identification information 390B. Surface acoustic wave strainsensor with identification information 390B, in turn, includes at leastan interdigital transducer 391B, and surface acoustic waveidentification (ID) information and surface acoustic wave strain sensorreflectors 393B. The spacing between the reflectors is used to obtainboth the strain data and the identification information. Strain sensor390B could also include an impedance matching network, as describedabove.

The location of reflectors 393B is illustrative only and is not intendedto be limiting to the specific location illustrated. For example, inplace of reflectors 393B being placed serially in a line along an x-axisas shown in FIG. 3B, the reflectors could be arranged in a stackedconfiguration (e.g., in two or more parallel rows) along the y-axis. Theparticular orientation is not essential so long as both identificationinformation and strain data can be generated.

FIGS. 3C, 3D, 3E and 3F, and 3G illustrate different implementations ofwireless package 370B. Similar implementations could be provided forwireless package 370A.

In FIG. 3C, wireless package 370B is implemented as a wireless package370B1. In wireless package 370B1, small folded antenna 380B1 and surfaceacoustic wave strain sensor with identification information 390B1 have acommon surface on a common substrate in wireless package 370B1, and arearranged serially along an x-axis. Small folded antenna 380B1 iselectrically connected to surface acoustic wave strain sensor withidentification information 390B1 by traces 391. Alternatively, theelectrical connection can be made with bond wire.

Strain sensor 390B1 includes an interdigital transducer IDT, andreflectors R1, R2. Reflector R1 is located a distance l₁ frominterdigital transducer IDT. Reflector R2 is located a distance l₂ frominterdigital transducer IDT. The transmitted surface acoustic wave isreflected first by reflector R1 and later by reflector R2. Changes instrain change the characteristics of the reflected surface acousticwaves. This change in characteristics of these waves is the strain dataand the strain data can be analyzed to provide force information.

The number and location of the reflectors in strain sensor 390B1 isillustrative only. Also, small folded antenna 380B1 is illustrated as aclosed loop antenna. This also is only illustrative and for example, afolded or a straight dipole antenna might be used. Further, the serialarrangement of antenna 380B1 and strain sensor 390B1 along an axis isalso only illustrative. Small folded antenna 380B1 might be positionedon any side of strain sensor 390B1, or on multiple sides of strainsensor 390B1 to have a common surface on the common substrate.

In another aspect, as illustrated in FIG. 3D, wireless package 370B isimplemented as wireless package 370B2. Small folded antenna 380B2 andsurface acoustic wave strain sensor with identification information390B2 are in separate sub-packages that are electrically connected toform wireless package 370B2. Thus, am all folded antenna 380B2 andsurface acoustic wave strain sensor with identification information390B2 are on separate and distinct substrates. Small folded antenna380B2 is connected to strain sensor 390B2 by electrical wires 392. Inone example, electrical wires 392 are a coaxial cable similar to thecoaxial cable used in an ultrasound transducer.

Wireless package 370B2 can be used, for example, when small foldedantenna 380B2 is too large to be mounted on the same distal portion ofthe surgical instrument as strain sensor 390B2. For example, strainsensor 390B2 could be mounted distal to wrist 220 (FIG. 2A), whileantenna 380B2 is mounted proximal to wrist 220. Also, the sub-packagecontaining small folded antenna 380B may be mounted separately onanother more proximal part of the jaw or on the larger wrist clevissurface since the surface area on the clevis side faces is more suitablefor a small folded antenna that may need to be larger than strain sensor390B2.

Strain sensor 390B2 also includes an interdigital transducer IDT, andreflectors R1, R2. Reflector R1 is located a distance l₁ frominterdigital transducer IDT. Reflector R2 is located a distance l₂ frominterdigital transducer IDT. The operation of strain sensor 390B2 issimilar to that described above for strain sensor 390B1. The number andlocation of the reflectors in strain sensor 390B2 is illustrative only.

Again, small folded antenna 380B2 is illustrated as a closed loopantenna. This also is only illustrative and for example, a folded ornon-folded dipole antenna might be used.

In FIGS. 3E and 3F, wireless package 370B is implemented as a wirelesspackage 370B3. FIG. 3E is a top view of wireless package 370B3 and FIG.3F is a bottom view of wireless package 370B3.

In wireless package 370B3, small folded antenna 380B3 (FIG. 3E) andsurface acoustic wave strain sensor with identification information390B3 (FIG. 3F) are on different surfaces of a common substrate inwireless package 370B3. For example, small folded antenna 380B3 (FIG.3E) is on a first surface 396 of substrate 395, while surface acousticwave strain sensor with identification information 390B3 (FIG. 3F) is ona second surface 397 of substrate 395. First surface 396 is opposite andremoved from second surface 397. Small folded antenna 380B3 is connectedto surface acoustic wave strain sensor with identification information390B3 by vias 394. In another aspect, antenna 380B3 and strain sensor390B3 may be on separate substrates, which are then laminated togetheras a stack having the two opposed surfaces.

Strain sensor 390B3 includes an interdigital transducer IDT, andreflectors R1, R2. Reflector R1 is located a distance l₁ frominterdigital transducer IDT. Reflector R2 is located a distance l₂ frominterdigital transducer IDT. The operation of strain sensor 390B3 issimilar to that described above for strain sensor 390B1

The number and location of the reflectors in strain sensor 390B3 isillustrative only. Also, small folded antenna 380B3 is illustrated as aclosed loop antenna. This also is only illustrative and for example, adipole antenna might be used.

FIG. 3G is an illustration of an implementation 390B4 of surfaceacoustic wave strain sensor with identification information 390B (FIG.3B). Surface acoustic wave strain sensor with identification information390B4 is a chirped surface acoustic wave strain sensor withidentification information and can be included in any of the wirelesspackages described herein.

Strain sensor 390B4 includes an interdigital transducer IDT, andreflectors R1 to R7. Reflector R1 is located a distance l₂ frominterdigital transducer IDT. Reflector R2 is located a distance l₂ frominterdigital transducer IDT. The distance between each pair ofreflectors as you move away from interdigital transducer IDT decreasesin this example. For example, the distance between reflectors (R1, R2)is greater than the distance between reflectors (R2, R3) and so forth.Alternatively, the distance between each pair of reflectors moving awayfrom interdigital transducer IDT could increase.

As an example, consider that sensor 390B4 is mounted on a needle driverand a needle is grasped in the vicinity of reflector R2. The forceapplied by the needle driver on the needle will change the shape of thelaw with respect to reflectors R1 to R2 and so change the distancesbetween these reflectors. However, the distances between reflectors R3to R7 are not changed. Thus, the strain data represented by the wavesreflected by each of reflectors R1 to R7 can be analyzed not only todetermine the force applied but also to determine the location of thatforce based on where the distance change between reflectors stopped.

As indicated above, the small folded antenna used in any of the wirelesspackages of FIGS. 3A to 3G can be a fractal (e.g. Hilbert, Sierpinski,etc.) antenna, a folded antenna designed using genetic algorithms, acrankline antenna, a micro-strip meander antenna, a compact diversityantenna or other minimum size antenna for a given wireless interrogationsignal. The particular antenna selected depends in part on whether abroad-band or narrow-band antenna is needed. A loop or dipole form ofthese antennas may be used. Where space permits, a non-folded antennamay be used.

As an example, one commercially available 2.4 GHz fractal monopoleantenna chip has a size of 3.7 mm by 2 mm, another has a size of 6.7 mmby 6.7 mm by 1 mm, and yet another has a size of 7 mm by 3 mm by 1 mm.Such antennas are available from Fractal. Antenna Systems, Inc., 130Third Ave., Waltham, Mass., U.S.A, and also from Fractus, S. A., Avda,Alcalde Barnils, 64-68. Sant Cugat del Vallés, 08174 Barcelona, Spain.

A particular antenna is chosen based upon the wireless interrogationsignal selected, the size of the antenna needed for the received andtransmitted signals, and the antenna properties including gain,impedance, directionality and the like. Also, the substratecharacteristics, if appropriate, and the mounting of a particularantenna are chosen to satisfy any ground plane requirements of thatantenna. If a particular antenna is not compatible with metal jaws,electrically non-conductive jaws, e.g., ceramic jaws, are utilized inthe surgical end effector. For example, ceramic jaws could be made ofany one of silicon nitride (SiN) and zirconia.

The selection of the frequency or frequency bandwidth of the wirelessinterrogation signal is based upon several factors. In one aspect, thefrequency or frequency bandwidth of the selected wireless interrogationsignal is above the upper harmonics of electro-cautery noiseinterference. The selected frequency or frequency bandwidth of thewireless interrogation signal functions with a surface acoustic wavestrain sensor and small folded antenna that have dimensions suitable formounting the wireless package in, which these elements are contained ona distal portion of a surgical end effector. The selected frequency orfrequency bandwidth of the wireless interrogation signal is compatiblewith other surgical and patient monitoring equipment used in theoperating room. In one aspect, the selected frequency or frequencybandwidth of the wireless interrogation signal has adequate signalstrength after penetrating through human tissue. In another aspect, theneed to penetrate human tissue is relaxed, as described more completelybelow.

Each of the surface acoustic wave strain sensors with identificationinformation in FIGS. 3A to 3G includes a piezoelectric substrate. In oneaspect, the piezoelectric substrate is selected from Quartz, LithiumNiobate, Lithum Tantalate, Lithium Tetraborate, Gallium Orthophospate,Lead Zirconate Titanate (PZT), Polyvinylidene Fluoride, and the LGXfamily of crystals including Langasite, Langanite and Langatate. Thislist of substrate materials is illustrative only and is not intended tobe limiting as other substrates that exhibit the piezoelectric effectmight be used.

Surface acoustic devices have been reported that included up to 96 bitsof identification information. In this aspect, at least enough bits ofidentification information are provided by the reflectors in the strainsensor to identify the type of the surgical instrument on which wirelessforce sensor 275 is mounted. In a further aspect, additional reflectorsare included to provide unique identification information to uniquelyidentify the specific surgical instrument within the type, e.g., providea serial number of the specific surgical instrument. As used herein,unique means that there is one and only one surgical instrument withthat identification information.

In one aspect, the surface acoustic wave strain sensor includesreflectors to provide 32 bits of identification information. The 32 bitsof identification information are sufficient to provide a uniqueidentity for up to 2³² different surgical instruments, i.e., 4.3×10⁹different surgical instruments. The particular number of bits used forthe identification information in the strain sensor is not critical solong as each surgical instrument of interest can be assigned a uniqueidentifier.

In some aspects, other identification information may be used ingenerating the unique identifier of the surgical instrument. Forexample, some surgical instruments include a non-volatile memory thatstores information that can be used, for example, to identify the typeof surgical instrument. For such a surgical instrument, the combinationof the identification information from the non-volatile memory and theidentification information from the surface acoustic wave strain sensorcan be combined to associate the strain information with the surgicalinstrument attached to a manipulator arm and correctly direct forceinformation to a surgeon using that surgical instrument.

Irrespective of the configuration of the wireless package containing thesurface acoustic wave strain sensor with identification information andthe small folded antenna, the wireless force sensor eliminates the needto route wires through difficult locations on the surgical instrument.In addition, since it is unnecessary to route wires to the force sensor,there is no need for additional electrical contacts at the sterileadapter interface, as described above.

FIG. 4A is a more detailed block diagram of aspects of an apparatus thatsupports a wireless force sensor 375B mounted on a surgical instrument.The apparatus of FIG. 4A can be used with any of the wireless forcesensors described herein.

Wireless package 370B of wireless force sensor 375B is mounted on adistal portion of a surgical instrument, as described above. Aconventional wireless interrogator 160A is connected to an interrogatorantenna 400 that sends a wireless interrogation signal to wirelesspackage 370B at transmission frequency TF. Wireless interrogator 160Athen switches to receive the wireless strain data and identificationinformation signal transmitted from wireless package 370B via antenna380B. Wireless interrogator 160A processes received radio frequencysignal RF and provides a digital signal to digital signal analysissystem 461 in control system 460 that in turn is in a control computer.

A processor, e.g., a digital signal processor, in control system 460performs an analysis of the digital signal to generate straininformation, to generate the unique identification, and to use thestrain information to generate and then output a force data signal. Theforce data signal is sent to an I/O device corresponding to the surgicalinstrument identified by the unique identifier and presented to surgeon190.

In one aspect, an indication of the force data signal, e.g., a movingbar graph, is presented in display 111 for the appropriate surgicalinstrument. In another aspect, the force data signal is used toactivate, for example, a pneumatically or electromagnetically actuatedpad on the master finger levers, which are used to control the surgicalinstrument with the unique identifier, to provide haptic force feedbackto surgeon 190 for that surgical instrument. In yet another aspect,actuators on the finger levers respond by applying a force on the masterfinger levers, which in turn apply force on the surgeon's fingers.Alternatively, or in some combination, an audible signal can be used toprovide force feedback to surgeon 190.

In some aspects, surface acoustic wave strain sensor with identificationinformation 390B may be sensitive to temperature. In addition to theeffects due to strain changes associated with applying loads to the law,temperature sensitivity can also affect the reflected waves.

Thus, in one aspect, it may be advantageous to use a calibration processin which forces are applied to the instrument jaws while the jams areheld at about human body temperature. Such a calibration process may bedone either by directly calculating the correction factors and offsetsor by a learning system such as a neural network embedded in thecalibration fixture or in the instrument itself. In any calibrationmethod, the calibration data may be programmed into an integratedcircuit embedded in the surgical instrument so that the surgical systemusing the individual instrument can correctly identify and apply itscorrection factors and offsets while the surgical instrument is in use.

In addition or alternatively, the temperature effects can be mitigatedby selection of the piezoelectric substrate and/or use of atemperature-compensated cut of the substrate material. Also, thesurgical instrument including wireless force sensor 375B can bemaintained in a stable thermal environment. For example, at least thedistal end of the surgical instrument can be maintained in a bath or ina shroud to keep the instrument at about human body temperature. In oneaspect, the shroud, e.g., radio-frequency shield pocket 255 (FIG. 2A),also shields the wireless force sensor from any interrogation signals.

In a surgical procedure prior to use, the surgical instrument is placedin such a human body temperature environment until the temperaturestabilizes and then is used in the surgery. If during surgery, thesurgical instrument is temporarily removed from the patient, the distalend of the surgical instrument is placed back in the temperaturestabilization device, which was referred to above as a shroud. In thisway, the temperature of the surface acoustic wave strain sensor remainssubstantially constant and so temperature effects are minimized. Inanother aspect, a chirped surface acoustic wave device (FIGS. 2E to 2Gand 3G) rejects a uniform temperature disturbance along the sensorbecause the temperature change shifts the entire frequency response ofthe chirped surface acoustic wave device while strain gradients alongthe law due to forces applied to the jaw widen or narrow the frequencyresponse.

In the above aspects, interrogator antenna 400 was outside the patient,and so the wireless signals have to penetrate the patient undergoingsurgery. However, in another aspect, an interrogator antenna 400B (FIG.4B) is mounted on a distal end of another surgical instrument, e.g.,endoscope 431, which is connected to wireless interrogator 160A by awired connection. Advantageously, such an antenna may be larger andoffer better coupling to the small folded surface acoustic wave strainsensor antenna.

Surgical instruments 430 and 431 are both used in the surgical operationand so are both within the patient during the surgery. During thesurgery, interrogator antenna 400B transmits the wireless interrogationsignal to wireless force sensor 475 mounted on a distal portion ofsurgical instrument 430.

Wireless force sensor 475 receives the wireless interrogation signal andin response thereto, transmits strain data and identificationinformation that is received by interrogator antenna 400B. The closerproximity of interrogator antenna 400B and wireless force sensor 475coupled with removing the need for the wireless signal to penetrate intoand out of the patient allows use of relatively weaker wireless signalstrengths. This may help to reduce any interference problems with otherinstruments or equipment used in the operating room or in adjacentoperating rooms.

Specifically, the low interrogation signal strength coupled with thefact that the interrogation signal is attenuated as the signalpenetrates out of the patient reduces the interrogation signal strengththat reaches the operating room or adjacent operating rooms. The reducedinterrogation signal strength in the operating rooms also reduces thelikelihood that wireless force sensors on different surgical instrumentsin the operating room or in adjacent operating rooms may receive andrespond to the interrogation signal.

It is noted that various surgical instruments may be improved inaccordance with the present invention, including but not limited totools with and without surgical end effectors, such as laws, scissors,graspers, needle holders, micro-dissectors, staple appliers, tickers,suction irrigation tools, clip appliers, irrigators, catheters, andsuction orifices. Alternatively, the surgical instrument may comprise anelectrosurgical probe for ablating, or coagulating tissue. Such surgicalinstruments are available from. Intuitive Surgical, Inc. of Sunnyvale,Calif.

Various other locations of force sensors can be utilized on a surgicalinstrument. Referring to FIG. 5, a perspective view is shown of asurgical instrument 530 including a force sensor apparatus 500 operablycoupled to a distal end of a rigid shaft 510 and proximal to a wristjoint 521 in accordance with an embodiment of the present invention. Anend portion 520, such as a surgical end effector, is coupled to forcesensor apparatus 500 via wrist joint 521. A housing 550 is operablycoupled to a proximal end of rigid shaft 510 and includes an interface552 which mechanically and electrically couples instrument 530 to amanipulator assembly.

In an alternative embodiment, an instrument portion of a surgicalinstrument includes strain sensors that are used to measure force. FIG.6A shows a perspective view of a portion 600 of a surgical instrumentthat includes a shaft 610, wrist joints 612 and 614, and an end portion620 that may be used to manipulate a surgical tool and/or contact thepatient. The surgical instrument also includes a housing that operablyinterfaces with a robotic manipulator arm, in one embodiment via asterile adaptor interface. Applicable housings, sterile adaptorinterfaces, and manipulator arms are disclosed in U.S. patentapplication Ser. No. 11/314,040 filed on Dec. 20, 2005, and U.S.application Ser. No. 11/613,800 filed on Dec. 20, 2006, the fulldisclosures of which are incorporated by reference herein for allpurposes. Examples of applicable shafts, end portions, housings, sterileadaptors, and manipulator arms are manufactured by Intuitive Surgical,Inc. of Sunnyvale, Calif.

In one configuration, end portion 620 has a range of motion thatincludes pitch and yaw motion about the x- and y-axes and rotation aboutthe z-axis (as shown in FIG. 6A). These motions, as well as actuation ofan end effector, are done via cables running through shaft. 610 andhousing 650 that transfer motion from the manipulator arm 51.Embodiments of drive assemblies, arms, forearm assemblies, adaptors, andother applicable parts are described for example in U.S. Pat. Nos.6,331,181, 6,491,701, and 6,770,081, the full disclosures of which areincorporated herein by reference for all purposes.

It is noted that various surgical instruments may be improved inaccordance with the present invention, including but not limited totools with and without end effectors, such as laws, scissors, graspers,needle holders, micro-dissectors, staple appliers, tackers, suctionirrigation tools, clip appliers, irrigators, catheters, and suctionorifices. Alternatively, the surgical instrument may comprise anelectrosurgical probe for ablating, or coagulating tissue. Such surgicalinstruments are commercially available from Intuitive Surgical, Inc. ofSunnyvale, Calif.

In accordance the embodiment of FIGS. 6A to 6E, instrument portion 600includes sensors (e.g., strain gauges) mounted onto the exterior surfaceof shaft 610, oriented parallel to the longitudinal (lengthwise) axis ofthe shaft, termed the z-axis. The two axes perpendicular to the shaftare called the x- and y-axes. The signals from the sensors are combinedarithmetically in various sums and differences to obtain measures ofthree perpendicular forces (e.g., F_(x), F_(y), and F_(z)) exerted uponthe instrument tip and the torques (Tx, Ty) about the two axesperpendicular to the shaft axis (i.e., the x- and y-axes). Themeasurement of the forces is made independent of the orientation andeffective lever arm length of a wrist mechanism at the distal end of theinstrument. Forces exerted against end portion 620 are detected by theforce sensing elements, which may be operably coupled to servo controlvia an interrogator or a processor for transmitting these forces tomaster(s).

In the embodiment of FIG. 6A, eight strain gauges 601, 602, 603, 604,605, 606, 607, and 608 are mounted to the outer surface of shaft 610 orin shallow recesses near the outer surface and provide strain data ε₁,ε₂, ε₃, ε₄, ε₅, ε₆, ε₇, and ε₈, respectively. The primary strain sensingdirection of the gauges are oriented parallel to the z-axis. The eightstrain gauges are mounted in two groups of four, wherein the four gaugesin one group are spaced equally, 90 degrees apart around thecircumference of the shaft at one axial position (i.e., forming two“rings” of four strain gauges each).

One group of four (e.g., gauges 601, 603, 605, and 607) is mountedproximal to a wrist mechanism as close to a distal end of shaft 610 aspossible. The second group of four (e.g., gauges 602, 604, 606, and 608)is mounted at a chosen distance “l” from the first group of four (towarda proximal end of shaft 610) and aligned with them so that pairs ofgauges in the two groups are aligned with each other (i.e., gauges 601and 602, 603 and 604, 605 and 606, and 607 and 608 are aligned).

The z-axis force (F_(z)) including both surgical forces and wrist cableforces is found from the sum of the eight gauge outputs multiplied by afactor of EA/8, where E is the shaft material modulus of elasticity inthe z-axis direction, and A is the cross-sectional area of the shaft.The lateral forces along the x- and y-axes (F_(x), and F_(y)) at or nearthe tip are found from the difference of the gauge outputs of a pair ofgauges on opposite sides of the shaft and the difference between thepair differences along the shaft multiplied by a factor of EI/2rl, whereE is the shaft material modulus of elasticity in the z-axis direction, Iis the shaft section moment of inertia, r is the radius from the shaftaxis to the acting plane of the gauges, and l is the distance betweenthe two groups of four gauges The calculations of the forces are derivedfrom the following equations.

With respect to FIG. 6A,

E = σ/ɛ A = π(r_(o)² − r_(i)²) I = (π/4)(r_(o)⁴ − r_(i)⁴)σ = (F/A) + (Mr/I)ɛ = [ɛ₁  ɛ₂  ɛ₃  ɛ₄  ɛ₅  ɛ₆  ɛ₇  ɛ₈]  ${\overset{F_{x}}{\begin{bmatrix}1 \\{- 1} \\{- 1} \\1 \\0 \\0 \\0 \\0\end{bmatrix}}{{EI}/21}r\mspace{14mu} \overset{F_{y}}{\begin{bmatrix}0 \\0 \\0 \\0 \\1 \\{- 1} \\{- 1} \\1\end{bmatrix}}{{EI}/21}r\mspace{14mu} \overset{F_{z}}{\begin{bmatrix}1 \\1 \\1 \\1 \\1 \\1 \\1 \\1\end{bmatrix}}} - {{EA}/8}$

With respect to FIGS. 6B and 6C,

A=π(r _(o) ² −r _(i) ²)

I=(π/4)(r _(o) ⁴ −r _(i) ⁴)

σ=Mr/I

σ₁ =FLr/I

σ₂ =F(L+l)r/I

E=σ/ε=>ε=σ/E

ε₁ =F _(x) Lr/EI

ε₂ =F _(x)((L+l)r/EI

ε₂−ε₁ =−F _(x) lr/EI

ε₄−ε₃ =F _(x) lr/EI

(ε₄−ε₃)−(ε₂−ε₁)=2F _(x) lr/EI

Thus,

ε₁−ε₂−ε₃+ε₄)EI/2lr=F _(x)

ε₅−ε₆−ε₇+ε₈)EI/2lr=F _(y)

(ε₁+ε₂+ε₃+ε₄+ε₅+ε₆+ε₇+ε₈)EA/8=F _(z)

F_(x) and F_(y) are thus invariant with respect to L and invariant withrespect to temperature at steady state.

Advantageously, the measured transverse forces (F_(x), F_(y)) at theinstrument tip are independent of variations in the effective lever armlength due to wrist orientation changes or gripping position changes inthe end portion during surgery. The measured transverse forces are alsoindependent of changes in the z-axis forces especially those due to thevarying wrist cable tensions. Further, the measured transverse forcesare independent of both surgical and wrist friction induced torquesapplied distal to the combined groups of strain gauges. Finally, themeasured forces along the x- and y-axes are independent of temperaturechanges when at thermal equilibrium over all gauges. This may be seen byadding an equal temperature disturbance strain to all four gauges in theequations for F_(x) and F_(y) and noting that the disturbances cancel.Thermal transients during which gauge temperatures are unequal are notcompensated by this design although other measures may be taken to doso.

The measurements of the torques about the x- and y-axes (T_(x) andT_(y)) at the instrument tip are derived from the differences of thegauges paired across the shaft diameter and the sum of the pairdifferences along the shaft axis multiplied by a factor EI/4r, whereinonce again F is the shaft material modulus of elasticity in the axialdirection, I is the shaft section moment of inertia, and r is the radiusfrom the shaft axis to the acting plane of the gauges. Thus the forces(F_(x), F_(y), F_(z)) and torques (T_(x), T_(y)) exerted at theinstrument tip are measured without errors due to wrist orientation orthe location of a gripped tool such as a suture needle within laws ortissue held in a grasper, for example. Torque measurements about the x-and y-axes are also independent of temperature at steady state. Thecalculations of the torques are derived from the following equations.

With respect to FIGS. 6D and 6E in conjunction with FIG. 6A,

${{{{////}//}//}//}//{\overset{T_{x}}{\begin{bmatrix}0 \\0 \\0 \\0 \\{- 1} \\{- 1} \\1 \\1\end{bmatrix}}{{EI}/4}r\mspace{14mu} \overset{T_{y}}{\begin{bmatrix}1 \\1 \\{- 1} \\{- 1} \\0 \\0 \\0 \\0\end{bmatrix}}{{EI}/4}r}$ σ = Mr/I σ₁ = σ₂ = Tr/I E = σ/ɛ =  > ɛ = σ/Eɛ₁ = ɛ₂ = Tr/EI

Thus,

(ε₁+ε₂−ε₃−ε₄)EI/4r=T _(y)

(−ε₅−ε₆+ε₇+ε₈)EI/4r=T _(x)

While the embodiment described with respect to FIGS. 6A to 6E may beapplied to surgical instruments of many constructions, it is ofparticular value for use with anisotropic linear fiber reinforcedpolymer tubing, in one example, because all gauges are oriented parallelto the z-axis with constant and easily characterized elastic properties.Similar advantages may be gained with properly characterized wovenreinforced tubing, and the method is also applicable to uniform elasticproperty tubing.

In one example, various strain gauges may be used, including but notlimited to conventional foil type resistance gauges, semiconductorgauges, optic fiber type gauges using Bragg grating or Fabry-Perot,technology, or others, such as strain sensing surface acoustic wave(SAW) devices. Optic fiber Bragg grating (FBG) gauges may beadvantageous in that two sensing elements may be located along one fiberat a known separation, thereby only requiring the provision of fourfibers along the instrument shaft.

Both fiber technologies require an interrogator unit that decodes theoptically encoded strain information into electrical signals compatiblewith the computer control hardware or display means of the minimallyinvasive surgical system. A processor may then be used to calculateforces according to the signals from the strain gauges/sensors.

In one aspect, the fiber Bragg gratings and the optic fibers arereplaced with a wireless package including a small folded antenna and asurface acoustic wave strain sensor with identification information, asdescribed above. In this aspect, the identification information includesinformation that not only uniquely identifies the particular surgicalinstrument, but also identifies the location of the surface acousticwave strain sensor with identification information. This permitsassociating the strain information with a particular location on forcesensor 600. Alternatively, multiple surface acoustic wave based forcesensors could be distinguished by frequency of the signal from each ofthe force sensors.

The above description and the accompanying drawings that illustrateaspects and embodiments of the present inventions should not be taken aslimiting the claims define the protected inventions. Various mechanical,compositional, structural, electrical, and operational changes may bemade without departing from the spirit and scope of this description andthe claims. In some instances, well-known circuits, structures, andtechniques have not been shown or described in detail to avoid obscuringthe invention.

Further, this description's terminology is not intended to limit theinvention. For example, spatially relative terms such as “beneath”,“below”, “lower”, “above”, “upper”, “proximal”, “distal”, and the likemay be used to describe one element's or feature's relationship toanother element or feature as illustrated in the figures. Thesespatially relative terms are intended to encompass different positionsand orientations of the device in use or operation in addition to theposition and orientation shown in the figures. For example, if thedevice in the figures is turned over, elements described as “below” or“beneath” other elements or features would then be “above” or “over” theother elements or features. Thus, the exemplary term “below” canencompass both positions and orientations of above and below. The devicemay be otherwise oriented (rotated 90 degrees or at other orientations)and the spatially relative descriptors used herein interpretedaccordingly.

The singular forms “a”, “an”, and “the” are intended to include theplural forms as well, unless the context indicates otherwise. The terms“comprises”, “comprising”, “includes”, and the like specify the presenceof stated features, steps, operations, elements, and/or components butdo not preclude the presence or addition of one or more other features,steps, operations, elements, components, and/or groups.

All examples and illustrative references are non-limiting and should notbe used to limit the claims to specific implementations and embodimentsdescribed herein and their equivalents. The headings are solely forformatting and should not be used to limit the subject matter in anyway, because text under one heading May cross reference or apply to textunder one or more headings. Finally, in view of this disclosure,particular features described in relation to one aspect or embodimentmay be applied to other disclosed aspects or embodiments of theinvention, even though not specifically shown in the drawings ordescribed in the text.

Embodiments described above illustrate but do not limit the invention.It should also be understood that numerous modifications and variationsare possible in accordance with the principles of the present invention.For example, the number of strain sensors and their configuration mayvary but must allow for applicable force determinations and noiserejection. Furthermore, the embodiments of force sensor apparatusdescribed above may be integrated with a surgical instrument uponmanufacture as a non-separable part. Accordingly, the scope of theinvention is defined only by the following claims.

We claim:
 1. A surgical instrument comprising: a shaft having anexterior surface: a wrist joint coupled to the shaft; and a surgical endeffector mounted distal to said wrist joint, the surgical instrumentcomprising a jaw portion, the jaw portion having an external non-contactsurface bounding a contact surface, wherein a force sensor is mounted onthe non-contact external surface, the force sensor comprising: awireless package comprising a surface acoustic wave strain sensor and afolded antenna, the folded antenna being electrically coupled to thesurface acoustic wave strain sensor.
 2. The surgical instrument of claim1, wherein the jaw portion comprises an electrically non-conductivematerial.
 3. The surgical instrument of claim 1, wherein said surfaceacoustic wave strain sensor comprises a chirped surface acoustic wavestrain sensor.
 4. The surgical instrument of claim 1, wherein thesurface acoustic wave strain sensor includes identification informationof the surgical instrument.
 5. The surgical instrument of claim 4,wherein said identification information includes an identification of atype of said surgical instrument.
 6. The surgical instrument of claim 5,wherein said identification information further includes identificationinformation unique to said surgical instrument.
 7. The surgicalinstrument of claim 4, wherein said identification information includesidentification information unique to said surgical instrument.
 8. Thesurgical instrument of claim 1, further comprising: a radio-frequencyshield pocket mounted on said jaw portion of said surgical instrument.9. The surgical instrument of claim 1, further comprising: aninterrogator antenna configured to transmit wireless interrogationsignals to said wireless package, and to receive, from said wirelesspackage, a wireless signal; and a wireless interrogator, coupled to saidinterrogator antenna, to receive signals from said interrogator antenna.10. The surgical instrument of claim 9, wherein said interrogatorantenna is located external to a patient undergoing surgery.
 11. Thesurgical instrument of claim 9, further comprising: a computer connectedto said wireless interrogator to receive a signal including (1)identification information of said surgical instrument and (2) straindata from said jaw portion, and to convert said strain data into a forcesignal wherein said force signal is used to provide feedback to asurgeon operating said surgical instrument.
 12. The surgical instrumentof claim 1, wherein a plurality of force sensors are mounted onto theexterior surface of the shaft.
 13. A method comprising: receiving awireless interrogation signal in a wireless package, the wirelesspackage comprising a surface acoustic wave strain sensor and a foldedantenna, the folded antenna being electrically coupled to the surfaceacoustic wave strain sensor, wireless package being mounted an externalnon-contact surface of a jaw portion of a surgical instrument, theexternal non-contact surface bounding a contact surface of the jawportion; and transmitting from said wireless package, in response tosaid wireless interrogation signal, a wireless signal includingidentification information of said surgical instrument.
 14. The methodof claim 13, further comprising receiving, by an antenna of aninterrogator, the wireless signal including the identificationinformation; outputting, the interrogator in response to the receivedwireless signal including the identification information, a digitalsignal to a control system; and outputting, by the control system inresponse to the digital signal, force data to an input/output deviceidentified using the identification information.